Mechanical assessment of the JT-60SA TF Coils during seismic event

JT-60SA is a fusion experiment designed to contribute to the early realization of fusion energy, by providing support to the operation of ITER, by addressing key physics issues for ITER and DEMO and by investigating how to optimize the operation of the next fusion power plants. It is a combined project of Japan and Europe Satellite Tokamak Program, as part of the Broader Approach Agreement and it is to be built in Naka, using the infrastructure of JT-60U. This article describes the finite element analysis performed to assess the mechanical behavior of the TF Coils under the seismic load of the Naka site. One particular type of boundary conditions has been evaluated: the TF Coils are not energized, and all components are at room temperature. This represents the most demanding conditions for the magnet system, as the wedge structure does not add any stiffness and strength due to the lack of centripetal forces on the individual coils; moreover the elastic limit of materials are lower than in cryogenic conditions. The results show that both stresses and displacements are acceptable for the TF Coil system, and that sufficient margin is available. In addition, loads on some of the major components can be extracted: maximum forces in the TF Coils supports, and force distribution on the cryostat base of JT-60SA.